COVID-19 and abnormal uterine bleeding: potential associations and mechanisms.

The impact of COVID-19 on menstruation has received a high level of public and media interest. Despite this, uncertainty exists about the advice that women and people who menstruate should receive in relation to the expected impact of SARS-CoV-2 infection, long COVID or COVID-19 vaccination on menstruation. Furthermore, the mechanisms leading to these reported menstrual changes are poorly understood. This review evaluates the published literature on COVID-19 and its impact on menstrual bleeding, discussing the strengths and limitations of these studies. We present evidence consistent with SARS-CoV-2 infection and long COVID having an association with changes in menstrual bleeding parameters and that the impact of COVID vaccination on menstruation appears less significant. An overview of menstrual physiology and known causes of abnormal uterine bleeding (AUB) is provided before discussing potential mechanisms which may underpin the menstrual disturbance reported with COVID-19, highlighting areas for future scientific study. Finally, consideration is given to the effect that menstruation may have on COVID-19, including the impact of the ovarian sex hormones on acute COVID-19 severity and susceptibility and reported variation in long COVID symptoms across the menstrual cycle. Understanding the current evidence and addressing gaps in our knowledge in this area are essential to inform public health policy, direct the treatment of menstrual disturbance and facilitate development of new therapies, which may reduce the severity of COVID-19 and improve quality of life for those experiencing long COVID.

Limiting pre-menstrual endometrial Hypoxia Inducible Factor 2 Alpha may fine-tune endometrial function at menstruation.

CONTEXT: Heavy menstrual bleeding (HMB) is common and debilitating, but the precise endometrial mechanisms causing increased menstrual blood loss (MBL) remain undefined. We have previously identified a role for hypoxia in endometrial repair following progesterone withdrawal. OBJECTIVE: As hypoxia inducible factor 2 alpha (HIF2A) is known to alter vascular function in other tissues, we hypothesised that endometrial HIF2A is involved in pre-menstrual optimisation of endometrial function during the secretory phase to limit MBL. RESULTS: Women with objective HMB had higher endometrial HIF2A during the mid-secretory phase when compared to those with normal MBL (p=0.0269). In a mouse model of simulated menses, genetic or pharmacological manipulation of HIF2A did not significantly affect endometrial breakdown/repair, volume of MBL or endometrial hypoxia. However, 88% of Hif2a heterozygote mice reached early-full repair by 24h versus only 65% of wild-type mice. Mean MBL was 0.39 µl (±0.67) in Hif2a heterozygote mice versus 0.98 µl (±0.79) in wild-type mice. Conversely, when we increased HIF2A pre-menstrually, 11% reached early repair at by 8h versus 30% of vehicle-treated mice. Mean MBL was 2.61 µl (±1.10) in mice with HIF2A stabilisation and 2.24 µl (±1.14) in vehicle-treated mice. These non-significant but consistent trends indicate that increased endometrial HIF2A may contribute to delayed endometrial repair and HMB. CONCLUSIONS: Increased HIF2A in the secretory endometrium is unlikely to be sufficient to account for the phenotype of HMB, but limitation of HIF2 levels may optimise endometrial function at menstruation.